With the advent of extreme miniaturization in electronic components, many new types of devices and activities have become possible and even prevalent. For example, the use of many types of mobile devices that use radio frequency signals for connectivity has become routine. One such device is a cell phone, and another is a personal information device, i.e. a handheld computing device that is usable for tasks such as scheduling appointments as well as tasks such as communicating over a network with another user having a similar or other device.
While mobile computing devices such as those mentioned above, as well as others, confer many benefits on their users, there are certain limitations imposed by such devices that are not experienced with non-mobile devices. For example, one dominant problem associated with mobile devices is the problem of operational lifetime between battery charges. As the user uses a device, the device power source, typically a battery, becomes depleted, eventually falling below a level required for operation of the device. At such time, the user must recharge or rejuvenate the power supply before continuing to use the device. This requirement for battery renewal can be problematic for several reasons. First, if the battery becomes depleted unexpectedly, the user may be greatly inconvenienced if he or she was relying on the device for some functionality, such as emergency calling etc. Additionally, even if the user is aware of the depletion and responds by beginning to charge the battery, the device will generally not be mobile and usable until after the charge cycle is complete, decreasing the overall general usefulness of the device.
Today's mobile devices often recognize the limited capacity of battery power sources by incorporating certain power-saving features. Such features include activating a screen or other user interface element only when the device is actively used by a user. For example, a cell phone may always be ready to receive an incoming call, but the device display screen may remain dark or blank until a user receives a call. Some personal information devices also incorporate features to activate the device only when it is being held and used. Furthermore, many mobile devices incorporate a power switch so that the device may be entirely powered down for a desired period. For example, a cell phone user may turn the phone completely off when no calls are expected to be made or received. However, such measures do not take full advantage of environmental cues to reduce power consumption.
In addition, while battery technologies have advanced rapidly in past years, the current rate of battery technology development is not keeping pace with the increasing capabilities and power drain of mobile devices. Thus, although techniques such as those mentioned above have been useful in somewhat increasing mobile device battery life, device operational lifetimes continue to be fairly limited, and better mobile device power management techniques are required to further reduce battery consumption and increase device operational lifetimes.